JPH0691161B2 - Method for forming insulating film of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] An insulating layer between conductor wiring layers of a multilayer wiring structure is used as a polyphosphoric acid siloxane copolymer film or a double layer of a polyphosphoric acid siloxane copolymer film and an inorganic material film. It is formed as a film, thereby flattening the step due to the conductor wiring layer and preventing disconnection and short circuit of the wiring and generation of cracks in the insulating layer.

[Industrial application field]

The present invention relates to a multilayer wiring structure used in a semiconductor integrated circuit.

[Conventional technology]

As an insulating layer between conductor wiring layers of a multilayer wiring structure, conventionally, an inorganic substance such as silicon dioxide, silicon nitride, alumina, phosphor glass, or a resin such as polyimide or silicone has been used.

The inorganic material film will be described with reference to FIG. Since the inorganic material film 4 formed by vapor deposition or chemical vapor deposition (CVD) has poor step coverage, the steps due to the metal conductor wiring 2 and the upper and lower wiring connecting portions remain as they are.
Therefore, it is difficult to miniaturize the wiring on the insulating layer 4, and there is a problem that the wiring is cut 7 and the wiring is short-circuited 8.

Next, the resin film will be described with reference to FIG. Since the heat-resistant resin such as polyimide, which is spin-coated and heated to 250 ° C. to 350 ° C. and hardened, has a large film thickness, the insulating layer 3 can considerably flatten the step due to the wiring thereunder. The resin starts thermal decomposition at 500 ° C,
And there is a problem that it easily absorbs moisture.

Silicone resin soluble in organic solvent is also spin-coated 25
Heat to 0 ° C-350 ° C to cure. The resin film 3 can flatten the level difference considerably, and it is 1 at 500 ° C in a nitrogen stream.
No thermal decomposition occurs even when heated for hours. However, after connecting the upper and lower wirings 2 through the resin film 3, when the resist used for the window opening mask is ashed with oxygen plasma, or after heating for 1 hour at 500 ° C. There is a problem that cracks occur in the resin layer.

Further, even if these films are used in combination, the above problems cannot be completely solved.

[Problems to be solved by the invention]

A semiconductor device having a multilayer wiring structure has a problem that a step is formed in the insulating layer by the conductor wiring layer, so that the upper wiring is cut and short-circuited, and the insulating film is thermally decomposed and cracked by heating.

[Means for solving problems]

The above problem is a general formula (Wherein R represents hydrogen, a lower alkyl group or an aryl group, and n and m are positive integers), and the polyphosphoric acid siloxane copolymer is used as the wiring interlayer insulating layer. It can be solved by a semiconductor device.

〔Example〕

100 g of dimethyldichlorosilane and methyl dichlorophosphate
100 g and 200 ml of methyl isobutyl ketone are mixed at room temperature (20
(° C) and mixed with 50 ml of ion-exchanged water. After completion of dropping, the reaction solvent was heated at 200 ° C. for 10 hours to carry out a polymerization reaction. The reaction solution was dried by removing the solvent gradually. The product thus obtained is a reddish brown solid, has a weight average molecular weight of 1 × 10 ⁴ , and has a w / n
Was 1.6.

This compound infrared absorption spectrum, absorption relates siloxane around 1100 cm ^-1 were observed absorption relates phosphate in the vicinity of 1020 cm ^-1. Also, from thermogravimetric analysis in an oxygen atmosphere, thermal oxidation of Si—CH _{3 at} around 380 ° C. and P at around 550 ° C.
Thermal oxidation of —O—CH ₃ was observed, confirming that the product was a polyphosphoric acid siloxane copolymer.

As shown in FIG. 1, (a) the film thickness on the silicon substrate 1.
An aluminum wiring layer 2 having a thickness of 1.0 μm was formed, and (b) a 35 wt% solution of the polyphosphoric acid siloxane copolymer in methyl isobutyl ketone was spin-coated at 3,000 rpm. This is heated at 120 ° C for 10 minutes to dry, and then at 450 ° C for 1 minute.
Heated and cured for hours. The film thickness thus formed 1.2 ~
(C) A phosphor glass (PSG) film 4 having a thickness of 1.0 μm was formed on the cured film 3 having a thickness of 1.5 μm by CVD. (D) Next, in order to connect the first wiring layer and the second wiring layer, the through hole 6 is formed by etching the insulating layer with CF ₄ plasma using the photoresist (product name AZ1350J) 5 as a mask. (E) The resist 5 was removed by oxygen plasma, and (f) aluminum 2 having a film thickness of 1.0 μm to be the second wiring layer was further formed by vapor deposition and connected to the aluminum of the first wiring layer. The multilayer wiring structure manufactured in this manner did not show a leak current even when a voltage of 25 V was applied.

Example 2 Example 1 except that no inorganic film is formed in step (c)
A multilayer wiring structure was manufactured in the same manner as in. This multilayer wiring structure did not show a leak current even when a voltage of 20 V was applied.

Comparative Example 1 Similar to Example 1, except that the step (b) of Example was not performed, the film thickness between the first wiring layer and the second wiring layer was 1.0.
A μm phosphorous glass film 4 was formed by CVD to manufacture a multilayer wiring structure. It showed a leak current close to 1mA at a voltage of 13V.

Comparative Example 2 A multilayer wiring structure was manufactured in the same manner as Comparative Example 1 except that the phosphorus glass film 4 was formed by vapor deposition. 1 at 10V
It showed a leakage current exceeding mA.

〔The invention's effect〕

The copolymer film of the present invention is capable of flattening the step due to the conductor wiring layer located thereunder, thus causing no disconnection and short circuit of the wiring, and not thermally decomposing at 500 ° C.,
No crack occurs even if the film thickness is 500 μC and 10 μm.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a multilayer wiring structure of the present invention, and FIG. 2 is a sectional view of a multilayer wiring structure having only a copolymer as an insulating layer, which is another embodiment of the present invention. FIG. 3 is a cross-sectional view of a conventional multi-layer wiring structure using only an inorganic material as an insulating layer. 1 ... Substrate, 2 ... Conductor wiring layer, 3 ... Polyphosphoric acid siloxane copolymer film, 4 ... Inorganic substance film, 5 ... Resist, 6 ... Window, 7 ... Wiring cut, 8 ... … Short wiring.

Front page continuation (72) Inventor Yoko Kawasaki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (2)

[Claims] 1. A general formula (Wherein R represents hydrogen, a lower alkyl group or an aryl group, and n and m are positive integers), and the polyphosphoric acid siloxane copolymer is used as the wiring interlayer insulating layer. Semiconductor device. 2. A homopolymer of the polyphosphoric acid siloxane copolymer,
The semiconductor device according to claim 1, wherein a wiring interlayer insulating layer is formed of a combination of this and an inorganic substance.